Merge pull request #155 from goffrie/source-maps

Source maps for callbacks mode
Support array syntax properly for callback!='_'.
Add a stack trace handler for _node and _coffee.

Works only in callbacks mode (of course) and doesn't support caching
yet.
Take source maps into account when generating stack frames.

This only affects _coffee for now. It should consistently generate
stack traces that refer to line numbers in the original files.
Generate source maps in fibers mode.
Improve source map generation for callbacks and fix a bug.

`indent` has to take a SourceNode; in one case it was being given a
string (for object literals with { "string key": val }).